Tool for removing concentric knockouts

ABSTRACT

A tool for removing concentric ring knockouts from electric wire junction and terminal boxes, etc., after removal of the center disc knockout. The tool has opposed groove defining gripping means set at an acute angle relative to each other which engage opposite points on the ring knockout so as to fracture the knockout by a back and forth movement of the tool until the points of connection of the ring knockout with the rest of the box fracture.

United States Patent 1,482,989 2/1924 Hering Inventor Frank W. Pepe 637 Prospect Drive, Lordship, Conn. 706,899

Feb. 20, 1968 May 25, 1971 Appl. No. Filed Patented TOOL FOR REMOVING CONCENTRIC KNOCKOUTS 13 Claims, 14 Drawing Figs.

US. Cl 29/267, 29/280, 8 1/3. 46

111:. CI 323p 19/04 Field of Search 29/267,

268, 280, 282, 283; 254/131; 72/(Inquired); 8I/3.I, 3.46 (A) References Cited UNITED STATES PATENTS 3,275,299 9/1966 Meshew 254/131 FOREIGN PATENTS 935,617 8/1963 Great Britain 81/3.46(A) Primary Examiner-William S. Lawson Assistant ExaminerLeon Gilden Attorney-Martin D. Wittstein ABSTRACT: A tool for removing concentric ring knockouts from electric wire junction and terminal boxes, etc., after removal of the center disc knockout. The tool has opposed groove defining gripping means set at an acute angle relative to each other which engage opposite points on the ring knockout so as to fracture the knockout by a back and forth movement of the too! until the points of connection of the ring knockout with the rest of the box fracture.

PATENTED EH25 I97! SHEET 1 OF 2 52 5O 65 mvmwm.

Frank TM Pepe A T TORNE Y PATENTEnmzslsn 3,679,797

saw a or 2 I-NVENTOR. ,Frank W Pepe BY 1 mm ATTORNEY 1 TOOL FOR REMOVING CONCENTRIC KNOCKOUTS BACKGROUND OF THE INVENTION This invention relates to a novel electrician's handtool and more particularly to a tool for removing concentric ring knockouts from electric junction boxes and the like.

In the construction industry it is well known that substantially all wiring of buildings, both commercial and residential, is initiated, coupled and/or terminated in metal boxlike enclosures such as fuse boxes, junction boxes, terminal outlet or switch boxes, and the like, all of which take a large variety of shapes and sizes depending on the location and function of the boxes. In standard practice, according to most electrical wiring codes, all electric wires must be connected either to utility or control components, or to each other, within these boxes which are customarily secured to a suitable surface and provided with some type of cover member so that wire connections or ends are not readily accessible.

In order to provide access to the interior of the boxes for the wires entering or leaving a particular box, as the case may be, the boxes are provided with a number of apertures, usually on all sides thereof except on the cover member. These apertures are initially closed by frangible or removable knockout members which maintain the sides of the box closed until itis desired to insert a wire therethrough. These members take a variety of forms and shapes; however, most must be broken, fractured or otherwise mutilated in order to remove them.

In order to eliminate any tension or pull on the terminal connections of wire within the box, the wires are secured to the side of the box where they pass through an aperture. This is usually accomplished by providing a socket which is secured within the aperture in the side of the box, the socket itself having screws or other suitable means for tightly gripping the outer covering or sheath of the wires.

Since electric wire is manufactured in different ways, e.g., plastic insulated, flexible helically wound metal sheathed (known in the trade as BX cable) and rigid pipe or conduit enclosed, it is necessary to have holding sockets of varying diameter to accommodate the particular type of wire being used. It is therefore necessary to have apertures with correspondingly varying diameters to accommodate the sockets.

In order to avoid duplication of boxes simply to provide apertures of the proper diameter, it has become customary to manufacture such boxes with large apertures having a type of closure member therefore which will provide one of two aperture sizes depending on the manner of removal of the aperture closure member. Such a member is generally known as the concentric knockout and generally comprises a circular disc defined by a score or weakened line on the side of the box extending over almost a complete circle, but discontinued over a short arc to provide a small nonweakened connecting portion for the disc to rest of the box side. A concentric ring knockout is defined by a concentric score or weakened line which extends in two almost semicircular but unjoined arcs around the disc, adjacent ends of each concentric are being connected to the inner circle where the latter terminates at the nonweakened connecting portion. Thus the ring knockout does not interfere with a connecting bridge now defined between the box side and the disc and is itself connected to the box side at a nonweakened point diametrically opposed from the disc connecting bridge. By selectively removing either the disc alone or the disc and concentric ring it is possible to obtain an aperture having either of two predetennined diameters which, by appropriate selection of sizes, will accommodate most commercial wire sizes.

These knockouts are customarily removed by a complicated procedure which requires placing a screwdriver or similar blunt instrument on the disc knockout and striking it with a hammer until the disc is sufficiently fractured from the box side and from the ring knockout to permit the disc to be manually bent back and forth until it is completely fractured. The tip of the screwdriver is then placed under the ring knockout at a point 90 from the point of nonweakened connection between the ring and the box side and, by using the opposite side of the aperture as a fulcrum, the screwdriver is forced downwardly so that the first mentioned side of the ring is broken from the box side and bent upwardly as much as possible. This procedure is repeated with the screwdriver tip under the of the aperture as a fulcrum. A pliers is now used to press the two upwardly bent halves of the ring knockout together and to bend them back and forth until the points of nonweakened connection is broken to permit complete removal of the ring. This procedure is awkward, time consuming and requires the use of several tools.

BRIEF SUMMARY OF THE INVENTION The present invention overcomes to a large extent many of the disadvantages of the foregoing knockout removal procedure, and completely eliminates certain other disadvantages thereof, by providing a single, easy to manipulate and effective tool for removing the above-described knockouts. The tool of the present invention is principally designed for the easy removal of the concentric ring knockout, but in one form of the invention it is intended and designed for the removal of both disc and ring knockouts. I

In its broader aspects, the principles of the present invention are embodied in a tool having an elongate body member with a handle portion at one end thereof and spaced-apart means at the other end of the body member for gripping diametrically opposite portions of the ring knockout after the center disc' portion has been otherwise removed, and there are means mounting the spaced-apart gripping means for relative movement with respect to each other so that the spaced apart gripping means can be inserted into the aperture fonned by removal of the center disc and sequentially engaged with the diametrically opposite portions of the ring knockout.

In some of its more limited aspects, the tool of the present invention comprises a pair of oppositely facing groovelike gripping means which are spaced-apart by a distance approximately equal to the internal diameter of the ring knockout, the opposite surfaces of the gripping means being adapted to engage and grip diametrically opposed arcuate portions of the opposite flat surfaces of the ring knockout. Preferably the groove forming surfaces are formed in such a way that planes passing through the grooves intersect at an acute angle and at a location between the grooves,'with a surface portion of the body member substantially coincident with the intersection of these planes forming a fulcrum adapted to rest on other portions of the ring knockout and about which the tool oscillates after it is engaged in operative position.

Means are provided for mounting at least one of the groovelike gripping means on the body member for movement relative to the other gripping means so that the movable gripping means can be moved away from a normal, operative position of engagement to permit insertion of the working end of the tool into the ring defining aperture, after which the movable gripping means is returned to its normal or operative position. This later mounting means may be either manually actuated or automatically actuated in response to insertion of the working end of the tool into the aperture. The construction and arrangement of the parts may also be such that the movable gripping means oscillates about a horizontal or vertical axis relative to the body member or reciprocates axially of the body member.

In one form of the invention, the tool is further provided with a means for removing the center disc knockout prior to engagement with the ring knockout, this means preferably taking the form of a boss or wedge-shaped projection at or near the working end of the tool and having a striking surface whereby the tool can be used in the manner of a hammer to fracture the disc knockout from the ring knockout.

Having briefly described the general nature of the present invention, it is a principal object thereof to provide a novel handtool for the removal of concentric ring knockouts from electrical junction boxes and the like.

Another object of the present invention is to provide a single handtool for removing concentric knockouts which performs all of the functions required to remove the knockouts, which functions presently require the use of three individual handtools.

It is another object of the present invention to provide a handtool for removing concentric ring knockouts which simultaneously grips diametrically opposite portions of a ring knockout so that the ring can be bent back and forth by an oscillating movement of the tool in order to fracture the knockout from the surrounding material.

It is a further object of the present invention to provide a handtool for removing concentric ring knockouts in which the working end of the tool is insertable in the ring defining aperture to engage the ring knockout from within the aperture.

It is still another object of the present invention to provide a handtool for removing concentric ring knockouts which can be used to remove the center disc knockout from the ring knockout before removal of the latter.

It is still a further object of the present invention to provide a handtool for removing concentric ring knockouts which is rugged in construction, inexpensive to manufacture and simple to operate.

These and other objects and advantages of the present invention will be more readily appreciated by an understanding of the following detailed description of preferred embodiments of the present invention when considered in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of one embodiment of the handtool of the present invention;

FIG. 2 is a fragmentary plan view of the tool shown in FIG.

FIG. 3 is a fragmentary side elevation of the tool shown in FIG. 1;

FIG. 4, 5 and 6 are progressive side views showing the manner of use of the tool shown in FIG. I to remove a concentric ring knockout;

FIG. 7 is a fragmentary perspective view of another embodiment of the invention;

FIG. 8 is a fragmentary side view of the tool shown in FIG. 7;

FIGS. 9 and 10 are progressive views showing the manner of use of the tool shown in FIG. 7 to remove a concentric ring knockout;

FIG. 11 is a fragmentary plan view of still another embodiment of the invention;

FIG. 12 is a sectional view taken on the line 12-12 of FIG. 1 1;

FIG. I3 is afragmentary plan view of a further embodiment of the invention; and

' FIG. I4 is a fragmentary side view of the embodiment shown in FIG. 13.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings and particularly to FIG. 4 thereof, there is shown a fragmentary portion of an electrical junction box 10 or the like in connection with which the tool of the present invention is intended to be used for the removal of concentric ring knockouts formed in the several walls of the box 10.

The general knockout construction 12 comprises a center circular disc 14 defined by a weakened or score line 16 formed in the wall 18 of the box, the weakened line I6 extending over almost a complete circle but being discontinued over a small arc 20 to provide a short nonweakened connecting portion 21 for the disc 14 to the rest of the wall 18. A ring knockout 22 is formed by a concentric score or weakened line which extends in two almost semicircular arcs 24 and 26. The arcs 24 and 26 are unjoined and terminate at one location 28 in order to provide a nonweakened connecting portion between the ring 22 and the rest of the wall 18; the arcs 24 and 26 are also unjoined at a diametrically opposite location 30 where adjacent ends of the arcs 24 and 26 are connected to the adjacent ends of the inner circle 16, thereby discontinuing the ring knockout 22 so that the latter does not interfere with the connection portion 21 between the center disc 14 and the rest of the box wall 18. By this construction both the disc 14 and the ring 22 are independently integrally connected to the wall 18 so that the disc 14 can be removed without in any way damaging or displacing the ring 22 if a small size aperture is desired.

It will be seen by reference to the portion of the wall 34 shown in cross section in FIG. 4 that the disc and ring knockouts may be easily and preferably formed by punching the ring knockout slightly out of the plane of the wall 34 except at the connection locations 21 and 28, while maintaining the disc knockout 14 in the plane of the wall 34. The weakened lines defining the knockouts may be formed by other known metal working operations.

Referring now to FIGS. 1 through 3, one embodiment of the tool 40 of the present invention comprises an elongate body member 42 having a suitable handle 44 on one end of the body member. The other working end of the body member is provided with an integrally formed widened head portion 46 which has generally rectangular dimensions such that the head portion 46 is larger than the internal diameter of the ring knockout for which the tool is designed so that the head portion cannot pass through the aperture formed by removal of the disc knockout.

The head portion has generally parallel top and bottom surfaces 48 and 50 respectively, and is provided with a bore 51 which passes vertically through the head portion 46 perpendicular to the surfaces 48 and 50. A relatively smaller or narrower nose portion 52 is integrally formed with the head portion 46 and defines the foremost end of the body member 42. The nose portion 52 is cut away adjacent its front upper edge 54 so as to define, with the front lower edge 56 of the head portion, a groove or recess 58 which extends over a short are of the front edge 56 of the head portion 46. This groove defines a first gripping means for engaging and gripping an arcuate portion of the opposite surfaces of the ring knockout 22 as will more clearly be seen hereinafter.

As best seen in FIG. 3, a shaft 60 extends through the bore 51 and terminates upwardly in a threaded end 62 which projects beyond the surface 48. A hand nut 64 is threadedly locked to the shaft 60 for rotating the latter for a purpose hereinafter made clear. The lower end of the shaft 60 is provided with a radially extending arcuate projection 66 which abuts the lower surface 50 of the head portion 48 so that the shaft 60 cannot pass through the bore 51.

The lower end of the shaft 60 is also provided with a second radially extending arcuate projection 68 which extends beyond the arcuate projection 66 so that the projections 68 and 66, together with the lower surface 50 of the head portion 46 effectively define another groove or channel 70 which also extends over a short arc. The groove 70 defines a second gripping means for engaging and gripping an arcuate portion of the opposite surfaces of the ring knockout 22 at a location diametrically opposite the location of engagement by the groove 58 as will be more clearly seen hereinafter.

It will be observed from FIG. 3 that the grooves 58 and 70 are disposed with respect to each other such that planes passing longitudinally through the respective grooves intersect to form an acute angle, substantially 45. The line of intersection lies substantially in the lower surface 50 of the head portion 46 and locates a fulcrum about which the tool is oscillated.

The hand nut 64 is provided with indicia such as OPEN and LOCK" as seen in FIG. 2, this indicia cooperating with an indicator such as the detent or colored dot 72, in order to indicate whether the groove 70 formed by the projection 68 on the bottom of the shaft 60 and the lower surface 50 of the head portion 46 is in an open or locked position. The groove 70 is in the open position, as shown in FIG. 2, when the groove is facing in the same direction as the groove 58. The groove 70 is in the locked position, as shown in FIG. 5, when it is facing in the opposite direction from the groove 58;

The handtool of this invention may preferably, though not necessarily, be provided with a wedge-shaped projection 75 which extends from one side of the head portion 46. This projection may take any desired or convenient shape and is provided for the purpose of knocking out the center disc 14 by using the hand tool 40 in the manner of a conventional hammer.

In the use of the handtool of the present invention, and referring to FIGS. 4 through 6, it will be seen that the hand nut 64 is rotated to set the groove 70 which defines the second gripping means so that it faces forwardly, i.e., in the same direction as the groove 58 which defines the first gripping means, this position being conveniently indicated by the indicia on the hand nut. The center disc knockout I4 is the head portion 46 is generally larger than the diameter of the aperture 74, it will not pass through the aperture after the recess 58 is engaged with the ring knockout, but rather will contact the ring knockout at the connecting locations 21 and 28. The tool is then' rotated in the direction of the arrow 73 about the connecting locations 21 and 28 as a fulcrum in order to simultaneously lower the projection 66 of the shaft 60 into the aperture 74 and to force that part of the ring knockout 22 which is engaged by the groove 58 upwardly to the position shown in FIG. 5. The two halves of the ring knockout separated by the connection locations are now disposcd at substantially a 45 angle to each other.

When the tool has been rotated to the position shown in FIG. 5 where the lower surface 50 of the head portion 46 contacts the ring knockout 22, the hand nut 64 is again rotated I80 in order to set the groove 70 in the locked position as indicated by the indicia on the hand nut. The groove 70 now faces away from the groove 58 so that it engages the ring knockout 22 and grips the latter in the'same manner as the groove 58. The tool is now rotated in the opposite direction as indicated by the arrow 76 about the connecting locations 21 and 28, the portion of the ring knockout gripped by the groove 70 being bent upwardly and the portion of the ring knockout gripped by the groove 58 being bent downwardly substantially to its initial position. By oscillating the tool up and down in the manner described, the ring knockout 22 will ultimately be fractured from the wall 18 of the box at the connecting locations 21 and 28 and can then be removed therefrom and discarded. It generally requires about five or six oscillations to fracture the ring knockout 22 from the wall.

It will be seen from the foregoing description of this embodiment of the invention and its manner of use that the shaft 7 and hand nut 64 constitute a means for mounting the second gripping means on the body member for movement relative to the first gripping means so that both gripping means can be inserted into the aperture 74 and sequentially engaged with opposite portions of the ring knockout 22. In this embodiment of the invention the movement of the second gripping means is rotary about a vertical axis relative to the head portion 46. As will be seen hereinafter, it is within the scope of this invention to provide other forms of movement of the second gripping means and also to have the first gripping means movable relative to the second. Also, the movement of either of the gripping means may be either manually accomplished as in the embodiment above described or it'may be automatic in that the relative movement is a function responsive to inserting the tool into the aperture defined by the ring knockout.

FIGS. 7 and.8 shown an embodiment of the invention in which the second gripping means oscillates about a horizontal axis relative to the head portion of the tool and does so for engagement in response to insertion of the tool into the aperture. More particularly, the tool comprises a body member 142 having a head portion 146 generally similar to the head portion 46 of the embodiment of FIG. 1. A first gripping means is defined by the groove 158 formed in the nose portion 152 and again disposed at approximately a 45 angle to the lower surface 150 of the head portion 146. The head portion 146 is provided with a vertically extending bore 151 in which is positioned a shaft 160. The shaft is pivotally connected to the head portion 146 by a pin 161 passing horizontally through the head portion 146 and the shaft 160.

Formed integrally with the lower end of the shaft 160 is a radially extending projection 168 which, together with the lower surface 150 of the head portion 146, defines the circular groove 170 which is the second gripping means. The projection 168 is formed to have a spherical lower surface 169 which fonns a camming surface to pivot the shaft 160 and projection 168 about the pin 161 when the tool is inserted into the aperture, although any desired surface configuration or contour may be provided on the projection 168 which serves the intended purpose. A finger knob 164 is screwed or otherwise suitably secured to the upper end of the shaft 160 in order to facilitate removal of the fractured ring knockout from the tool. In order to urge the shaft 160 and the projection 168 into an operative position, a compression spring is provided in a bore 182 formed in the head portion 146 above the level of the pivot pin 161 whereby the spring 180 continuously urges the shaft 160 in a direction to maintain the groove I70 away from the groove 158. It will be also observed that the bore 151 is tapered outwardly in opposite directions from the pivot pin 161 in order to permit the shaft 160 to pivot freely.

The manner of use of this embodiment of the invention is shown in FIGS. 9 and 10 wherein it is seen that the nose portion 152 is inserted into the aperture 174 and the groove 158 is engaged with a portion of the ring knockout in the same manner as with the form of tool shown in FIG. 4. Thereafter, the tool is pivoted downwardly to a point where the spherical surface 169 contacts the inner edge of the ring knockout 22, after which further downward movement of the tool causes the shaft 160 and the projection 168 to be pivoted in a clockwise direction as viewed in FIG. 9, against the force of the spring 180 until the peripheral edge of the projection 168 clears the ring knockout 22. At that point the spring 180 pivots the shaft 160 in the opposite direction to cause the ring knockout 22 to be engaged and gripped within the groove 170. During the latter part of the movement of the tool, the portion of the ring knockout 22 which is engaged by the groove 158 is bent upwardly as seen in FIG. 10. After the tool is fully engaged with the ring knockout on both sides of the latter, the tool is used in the same manner as described above to fracture the ring knockout from the box wall. The ring knockout is easily removed from the tool by manually pulling rearwardly on the finger knob 164.

FIGS. 11 and 12 show another embodiment of the invention in which the second gripping means is movable relative to the first gripping means in a direction axially of the tool, again for engagement in response to the tool being inserted into the aperture. More particularly, the tool 240 comprises a body member 242 having an elongate head portion 246. A first gripping means is defined by the groove 258 formed in the nose portion 252 and again disposed at approximately a 45 angle to the lower surface 250 of the head portion 246.

The head portion 246 is provided with a vertically extending bore 251 which communicates with a horizontally extending recess 253, the latter being open at the bottom and being partially closed by a cover plate 255 which is removably secured to the head portion 246 as by screws 257. An L-shaped slide member 259 is positioned within the horizontal recess 253 and is made shorter in length than the recess in order to provide room for the member 259 to slide back and forth within the recess 253 while being supported for such movement by the cover plate 255. A vertical extension 263 of the slide member 259 projects downwardly through an opening 265 which is not covered by the cover plate 255, the opening 265 being long enough to permit movement of the extension 263. The extension 263 terminates in a radial projection 268 which, with the lower surface 250 of the cover plate 255, defines a groove 270 which is the second gripping means of this embodiment of the invention. As with the previous embodiment of the invention, the projection 268 is provided with a spherical surface 269 which acts as a camming surface in cooperation with the ring knockout 22 to move the slide member 255 forwardly upon insertion of the tool into the aperture during engagement of the groove 270 with the ring knockout.

In order to maintain the first and second gripping means in opposed operative relationship, the slide member is provided with a longitudinal bore 282 within which a spring 280 is located, the spring 280 pressing against the forward wall of the recess 253 to urge the slide member 255 rearwardly. The slide member 255 is also provided with a shaft 260 which is suitably secured to the slide member 255 and which projects upwardly through the bore 251, the shaft having a suitably smaller diameter than the bore 251, the shaft having a suitably smaller diameter than the bore so as to be able to slide back and forth within the bore. The shaft 260 is provided with a finger knob 264 to facilitate manual movement of the slide member 255 for removal of the fractured ring knockout therefrom.

The manner of use of this embodiment of the invention is substantially identical to that described above in connection with the embodiment shown in FIGS. 7 through 10 and further description thereof is not therefore deemed necessary.

A still further embodiment of the present invention is shown in FIGS. 13 and 14 in which the first gripping means is movable relative to the second gripping means, the latter being formed integrally with the head portion of the tool, with provision again being made for automatic engagement of the movable gripping means with the ring knockout. More particularly, the tool 340 comprises a body member 342 having a head portion 346 generally resembling the head portion of the embodiment shown in H6. 1. A vertical extension 363 is integrally formed with the head portion 346 adjacent the forward end of the latter, the extension depending from the lower surface 350 of the head portion and being provided with an arcuate radial projection 368'which, together with the lower surface 350 of the head portion, defines a groove 370 which forms the second gripping means of this embodiment of the invention.

The head portion 346 is bifurcated adjacent its front end to provide a slot 390 adapted to receive a bar 392 which is pivotally secured to the head portion 346 as by the pivot pin 361. The bar 392 is normally disposed with its longitudinal axis at about a 45 angle relative to the longitudinal axis of the body member by abutting a correspondingly sloped wall 393 of the slot 390. The bar is normally held in this position by a spring 380 which is connected to the upper rear end of the bar as at 394 and to the body member as at 395. In order to allow for counterclockwise movement of the bar 392 from the position shown, a portion 396 of the wall 393 is cut away at a steeper angle.

The lower forward end 352 of the bar 392 is provided with a forwardly facing arcuate groove 358 which is disposed at approximately a 45 angle relative to the groove 370 and which defines the first gripping means of this embodiment of the invention. It will now be understood that the first gripping means 358 is movable relative to the second gripping means 370. The projection 352 of the bar 392 is provided with a curved lower surface 369 which acts as a camming surface in conjunction with the inner edge of the ring knockout to pivot the bar 392 in a counterclockwise direction to permit insertion of the projection 352 into the aperture for engagement of the groove 358 with the ring knockout.

In using the tool shown in FlGS. 13 and 14, the tool is held substantially parallel to the wall of the box in which the ring knockout is to be removed, and the second gripping means 370 is first engaged with the ring knockout as will be understood from previous description. The tool is now raised, opposite portions of the lower surface 350 of the head portion pressing against the ring knockout at the connecting locations. As the tool is raised, the portion of the ring knockout engaged by the groove 370 is bent upwardly and the camming surface 369 engages the opposite side of the ring knockout to pivot the bar 392 in a counterclockwise direction against the force of the spring 380. Continued upward movement of the tool causes the groove 358 to engage and grip the ring knockout under the influence of the spring 380. The tool is then oscillated back and forth until the ring knockout is fractured from the box wall, after which it is removed from the tool by manually pushing forward on the upper end of the bar 392.

It is apparent from the foregoing that there is provided and disclosed herein a tool for removing concentric knockouts from the walls of electrical junction boxes which achieves the foregoing objects of the invention and which obviates the disadvantages of prior art methods of removing these knockouts. It is to be understood that the embodiments of the invention described and shown herein are merely illustrative of the best modes presently contemplated for carrying out the principles of the invention, the latter being intended to cover all such variations, modifications and equivalents thereof as may be encompassed within the scope of the claims appended hereto. What I claim and desire to secure by Letters Patent is:

Iclaim:

l. A tool for removing concentric ring knockouts from a relatively thin sheet member, said knockouts being defined by concentric weakened lines on said sheet member, said ring knockouts having a predetermined internal diameter and having portions integrally connecting the knockouts with said sheet member, said tool comprising A. an elongate body member having a handle portion at one end thereof,

B. spaced-apart oppositely facing sheet member gripping means disposed adjacent the other end of said body member for gripping opposite surfaces of diametrically opposite portions of a ring knockout, said gripping means being spaced-apart a predetermined distance corresponding substantially to said internal diameter of said ring knockouts, and

C. means mounting said spaced-apart gripping means for relative movement with respect to each other whereby said spaced-apart gripping means can be inserted into the aperture defined by the inner edge of said ring knockout and sequentially engaged with said diametrically opposite portions of the ring knockout.

2. A tool as set forth in claim 1 wherein said last-named means includes means for manually moving one of said spaced-apart gripping means relative to the other whereby said one spaced-apart gripping means is manually engageable and disengageable with its corresponding portion of the ring knockout.

3. A tool as set forth in claim 1 wherein said last-named means includes yieldable means normally urging one of said spaced-apart means away from the other whereby said one spaced-apart means is yieldably urged toward a position of operative engagement withits corresponding portion of the ring knockout.

4. A tool for removing concentric ring knockouts from a relatively thin sheet member, said knockouts being defined by concentric weakened lines on said sheet member, said ring knockouts having a predetermined internal diameter and having portions integrally connecting the knockouts with said sheet member, said tool comprising A. an elongate body member having a handle portion at one end thereof,

B. first sheet member gripping means disposed adjacent the opposite end of said body member for gripping a first arcuate portion of the opposite surfaces of a ring knockout,

C. second oppositely facing sheet member gripping means disposed adjacent said first gripping means but spaced from said first gripping means by a predetennined distance corresponding substantially to said internal diameter of said ring knockout for gripping a second arcuate portion of the opposite surfaces of the ring knockout at a location diametrically opposite said first arcuate portion, and I D. means mounting one of said gripping means on said body member for movement relative to the other of said gripping means to change said predetermined distance between said first and second gripping means to pcnnit said one gripping means to be inserted within the aperture defined bythe inner edge of said ring knockout and to engage the latter in gripping relationship after the other of said gripping means has been engaged with and. is gripping the ring knockout, whereby the ring knockout is bent back and forth and ultimately fractured from the sheet member by an oscillating movement of said tool.

5. A tool as set forth in claim 4 wherein said means mounting said one gripping means for movement includes manually operable means for moving said one gripping means toward and away from said other gripping means whereby said one gripping means can be moved away from an operative gripping position to permit insertion of said one gripping means within said aperture.

6. A tool as set forth in claim 4 wherein said means mounting said one gripping means for movement includes yieldable means normally urging said one gripping means away from said other gripping means whereby said one gripping means is urged toward an operative gripping position and means operable in response to movement of said tool to force said one gripping means toward said other gripping means whereby said one gripping means is moved away from said operative gripping position to permit insertion of said one means within said aperture.

7. A tool as set forth in claim 6 wherein said first and second gripping means are disposed in planes which define an acute angle relativeto each other whereby one of said arcuate portions of the ring knockout is bent by said other gripping means as the tool is oscillated to engage said one gripping means with the other of said arcuate portions of the ring knockout.

8. A tool as set forth in claim 9 wherein said body member has a surface portion disposed intennediate said first and second gripping means, said surface portion being disposed substantially at the juncture of the planes of said first and second gripping means and defining a fulcrum adapted to rest on the ring knockout substantially at the connecting portions between the ring knockout and the sheet member and about which said tool oscillates to bend the ring knockout.

9. A tool for removing concentric ring knockouts from a relatively thin sheet member, said knockouts being defined by concentric weakened lines on said sheet member, said ring knockouts having a predetermined internal diameter and having portions integrally connecting the knockouts with said sheet member, said tool comprising A. an elongate body member having handle portion at one end thereof, a

B. an enlarged head portion at the other end of said body member, said head portion having at least one surface having a predetermined dimension in relation to a ring knockout of a predetennined size such that said head portion will not pass through the aperture defined by the inner edge of said ring knockout,

C. a reduced nose portion adjacent the forward end of said head portion,

D. means on said nose portion defining a forwardly facing,

gripping relatively narrow groove shaped to receive and engage in substantially gripping relationship an arcuate portion of the opposite surfaces of said ring knockout,

E. a member extending laterally away from said one surface of said head portion and having a radially extending projection which, together with a portion of said one surface, defines a rearwardly facing relatively narrow groove shaped to receiye and engage in substantially grippin relationship a drametncally'opposite arcuate portion 0 the opposite surfaces of said ring knockout, said grooves being normally spaced apart a predetermined distance along said one surface substantially equal to the diameter of said aperture, and

F. means mounting one of said groove defining means on said head portion for movement relative to the other of said groove defining means between an operative engaging position and an inoperative nonengaging position to permit said one groove defining means to be inserted within said aperture and to engage the ring knockout in gripping relationship after the other of said groove defining means has been engaged with and is gripping the ring knockout, whereby the ring knockout is bent back and forth and ultimately fractured from the sheet member by an oscillating movement of said tool.

10. A tool as set forth in claim 9 wherein said mounting means comprises a shaft mounted in said head portion for rotation about an axis perpendicular to said one surface, said laterally extending member being formed integrally with said shaft, said radially extending projection extending over only an arc of a circle whereby rotation of said shaft moves said radially extending projection to said inoperative nonengaging position within the diameter of said aperture to permit said radially extending projection to be passed through said aperture..

11. A tool as set forth in claim 9 wherein said mounting means comprises a shaft mounted in said head portion for pivotable movement about an axis parallel to but spaced from said one surface of said head portion and perpendicular to the longitudinal axis of said body member, said laterally extending member being formed integrally with said shaft, whereby movement of said shaft in one direction about said axis moves said radially extending projection to said inoperative nonengaging position within the diameter of said aperture to permit said radially extending projection to pass through said aperture.

12. A tool as set forth in claim 9 wherein said mounting means comprises a slide member mounted in said head portion for sliding movement axially of said body member, said laterally extending member being formed integrally with said slide member, whereby movement of said slide member moves said radially extending projection to said inoperative nonengaging position within the diameter of said aperture to permit said radially extending projection to pass through said aperture.

13. A tool as set forth in claim 9 wherein said mounting means comprises a bar mounted in said head portion for pivotable movement about an axis parallel to but spaced from said one surface of said head portion and perpendicular to the longitudinal axis of said body member, said reduced nose portion with said groove defining means thereon being fonned integrally with said bar, whereby movement of said bar in one direction about said axis moves said groove defining means on said nose portion to said inoperative nonengaging position within the diameter of said aperture to permit said nose portion to partially pass through said aperture. 

1. A tool for removing concentric ring knockouts from a relatively thin sheet member, said knockouts being defined by concentric weakened lines on said sheet member, said ring knockouts having a predetermined internal diameter and having portions integrally connecting the knockouts with said sheet member, said tool comprising A. an elongate body member having a handle portion at oNe end thereof, B. spaced-apart oppositely facing sheet member gripping means disposed adjacent the other end of said body member for gripping opposite surfaces of diametrically opposite portions of a ring knockout, said gripping means being spaced-apart a predetermined distance corresponding substantially to said internal diameter of said ring knockouts, and C. means mounting said spaced-apart gripping means for relative movement with respect to each other whereby said spaced-apart gripping means can be inserted into the aperture defined by the inner edge of said ring knockout and sequentially engaged with said diametrically opposite portions of the ring knockout.
 2. A tool as set forth in claim 1 wherein said last-named means includes means for manually moving one of said spaced-apart gripping means relative to the other whereby said one spaced-apart gripping means is manually engageable and disengageable with its corresponding portion of the ring knockout.
 3. A tool as set forth in claim 1 wherein said last-named means includes yieldable means normally urging one of said spaced-apart means away from the other whereby said one spaced-apart means is yieldably urged toward a position of operative engagement with its corresponding portion of the ring knockout.
 4. A tool for removing concentric ring knockouts from a relatively thin sheet member, said knockouts being defined by concentric weakened lines on said sheet member, said ring knockouts having a predetermined internal diameter and having portions integrally connecting the knockouts with said sheet member, said tool comprising A. an elongate body member having a handle portion at one end thereof, B. first sheet member gripping means disposed adjacent the opposite end of said body member for gripping a first arcuate portion of the opposite surfaces of a ring knockout, C. second oppositely facing sheet member gripping means disposed adjacent said first gripping means but spaced from said first gripping means by a predetermined distance corresponding substantially to said internal diameter of said ring knockout for gripping a second arcuate portion of the opposite surfaces of the ring knockout at a location diametrically opposite said first arcuate portion, and D. means mounting one of said gripping means on said body member for movement relative to the other of said gripping means to change said predetermined distance between said first and second gripping means to permit said one gripping means to be inserted within the aperture defined by the inner edge of said ring knockout and to engage the latter in gripping relationship after the other of said gripping means has been engaged with and is gripping the ring knockout, whereby the ring knockout is bent back and forth and ultimately fractured from the sheet member by an oscillating movement of said tool.
 5. A tool as set forth in claim 4 wherein said means mounting said one gripping means for movement includes manually operable means for moving said one gripping means toward and away from said other gripping means whereby said one gripping means can be moved away from an operative gripping position to permit insertion of said one gripping means within said aperture.
 6. A tool as set forth in claim 4 wherein said means mounting said one gripping means for movement includes yieldable means normally urging said one gripping means away from said other gripping means whereby said one gripping means is urged toward an operative gripping position and means operable in response to movement of said tool to force said one gripping means toward said other gripping means whereby said one gripping means is moved away from said operative gripping position to permit insertion of said one gripping means within said aperture.
 7. A tool as set forth in claim 6 wherein said first and second gripping means are disposed in planes which define an acute angle relative to each other whereby one of said arcuate portions of the ring knockout is bEnt by said other gripping means as the tool is oscillated to engage said one gripping means with the other of said arcuate portions of the ring knockout.
 8. A tool as set forth in claim 9 wherein said body member has a surface portion disposed intermediate said first and second gripping means, said surface portion being disposed substantially at the juncture of the planes of said first and second gripping means and defining a fulcrum adapted to rest on the ring knockout substantially at the connecting portions between the ring knockout and the sheet member and about which said tool oscillates to bend the ring knockout.
 9. A tool for removing concentric ring knockouts from a relatively thin sheet member, said knockouts being defined by concentric weakened lines on said sheet member, said ring knockouts having a predetermined internal diameter and having portions integrally connecting the knockouts with said sheet member, said tool comprising A. an elongate body member having handle portion at one end thereof, B. an enlarged head portion at the other end of said body member, said head portion having at least one surface having a predetermined dimension in relation to a ring knockout of a predetermined size such that said head portion will not pass through the aperture defined by the inner edge of said ring knockout, C. a reduced nose portion adjacent the forward end of said head portion, D. means on said nose portion defining a forwardly facing, relatively narrow groove shaped to receive and engage in substantially gripping relationship an arcuate portion of the opposite surfaces of said ring knockout, E. a member extending laterally away from said one surface of said head portion and having a radially extending projection which, together with a portion of said one surface, defines a rearwardly facing relatively narrow groove shaped to receive and engage in substantially gripping relationship a diametrically opposite arcuate portion of the opposite surfaces of said ring knockout, said grooves being normally spaced apart a predetermined distance along said one surface substantially equal to the diameter of said aperture, and F. means mounting one of said groove defining means on said head portion for movement relative to the other of said groove defining means between an operative engaging position and an inoperative nonengaging position to permit said one groove defining means to be inserted within said aperture and to engage the ring knockout in gripping relationship after the other of said groove defining means has been engaged with and is gripping the ring knockout, whereby the ring knockout is bent back and forth and ultimately fractured from the sheet member by an oscillating movement of said tool.
 10. A tool as set forth in claim 9 wherein said mounting means comprises a shaft mounted in said head portion for rotation about an axis perpendicular to said one surface, said laterally extending member being formed integrally with said shaft, said radially extending projection extending over only an arc of a circle whereby rotation of said shaft moves said radially extending projection to said inoperative nonengaging position within the diameter of said aperture to permit said radially extending projection to be passed through said aperture.
 11. A tool as set forth in claim 9 wherein said mounting means comprises a shaft mounted in said head portion for pivotable movement about an axis parallel to but spaced from said one surface of said head portion and perpendicular to the longitudinal axis of said body member, said laterally extending member being formed integrally with said shaft, whereby movement of said shaft in one direction about said axis moves said radially extending projection to said inoperative nonengaging position within the diameter of said aperture to permit said radially extending projection to pass through said aperture.
 12. A tool as set forth in claim 9 wherein said mounting means comprises a slide Member mounted in said head portion for sliding movement axially of said body member, said laterally extending member being formed integrally with said slide member, whereby movement of said slide member moves said radially extending projection to said inoperative nonengaging position within the diameter of said aperture to permit said radially extending projection to pass through said aperture.
 13. A tool as set forth in claim 9 wherein said mounting means comprises a bar mounted in said head portion for pivotable movement about an axis parallel to but spaced from said one surface of said head portion and perpendicular to the longitudinal axis of said body member, said reduced nose portion with said groove defining means thereon being formed integrally with said bar, whereby movement of said bar in one direction about said axis moves said groove defining means on said nose portion to said inoperative nonengaging position within the diameter of said aperture to permit said nose portion to partially pass through said aperture. 